The Islamic calendar or Muslim calendar or Hijri calendar (Arabic: التقويم الهجري‎; at-taqwīm al-hijrī; Persian: تقویم هجری قمری ‎ taqwīm-e hejri-ye qamari; Turkish: Hicri Takvim) is a lunar calendar based on 12 lunar months in a year of 354 or 355 days, used to date events in many Muslim countries (concurrently with the Gregorian calendar), and used by Muslims everywhere to determine the proper day on which to celebrate Islamic holy days and festivals. The first year was the year during which the emigration of the Islamic prophetMuhammad from Mecca to Medina, known as the Hijra, occurred. Each numbered year is designated either H for Hijra or AH for the Latinanno Hegirae (in the year of the Hijra).[1] A limited number of years before Hijra (BH) are used to date events related to Islam, such as the birth of Muhammad in 53 BH.[2] The current Islamic year is 1431 AH, from approximately December 17, 2009 (evening) to December 6, 2010 (evening).Template:Update-after

Of all the months in the Islamic calendar, Ramadan is the most venerated. Muslims are required to abstain from eating, drinking any liquid, and sexual intercourse during the daylight hours of this month.

In the Arabic language, as in the Hebrew language, the "first day" of the week corresponds with Sunday of the planetary week. The Islamic and Jewish weekdays begin at sunset, whereas the medieval Christian and planetary weekdays begin at the following midnight.[4] Muslims gather for worship at a mosque at noon on "gathering day" (Yaum Al-Jumu'ah) which corresponds with Friday. Thus "gathering day" is often regarded as the weekly day of rest, so the following day, Saturday, is often regarded as the first day of the work week.

Some scholars, both Muslim[5][6] and Western,[7] think that the pre-Islamic calendar of central Arabia was a purely lunar calendar similar to the modern Islamic calendar, differing only when the sanctity of the four holy months were postponed by one month from time to time.

Other scholars, both Muslim[8][9] and Western,[10][11] concur that it was originally a lunar calendar, but about 200 years before the Hijra it was transformed into a lunisolar calendar containing an intercalary month added from time to time to keep the pilgrimage within the season of the year when merchandise was most abundant for Bedouin buyers. This intercalation was administered by the Nasa'a of the tribe Kinana, known as the Kalomis, the plural of Kalammas, who learned of it from Jews. The process was called Nasi or postponement because every third year the beginning of the year was postponed by one month. The intercalation doubled the month of the pilgrimage, that is, the month of the pilgrimage and the following month were given the same name, postponing the names and the sanctity of all subsequent months in the year by one. The first intercalation doubled the first month Muharram, then three years later the second month Safar was doubled, continuing until the intercalation had passed through all twelve months of the year and returned to Muharram, when it was repeated. Support for this view is provided by inscriptions from the south Arabian pre-Islamic kingdoms of Qataban (Kataban) and Sheba (Saba) (both in modern Yemen), whose lunisolar calendars featured an intercalary month obtained by repeating a normal month. The prohibition of Nasi was revealed when the intercalated month had returned to its position just before Nasi began.

If Nasi meant intercalation, then the number and the position of the intercalary months between 1 AH and 10 AH are uncertain, western calendar dates commonly cited for key events in early Islam such as the Hijra, the Battle of Badr, the Battle of Uhud and the Battle of the Trench, should be viewed with caution as they might be in error by one, two or even three lunar months.

In the tenth year of the Hijra, as documented in the Qur'an (sura 9:36-37), Allah - God the Almighty revealed the prohibition of the Nasi.

The number of months with Allah has been twelve months by Allah's ordinance since the day He created the heavens and the earth. Of these four are known as forbidden [to fight in]; That is the straight usage, so do not wrong yourselves therein, and fight those who go astray. But know that Allah is with those who restrain themselves.

Verily the transposing (of a prohibited month) is an addition to Unbelief: The Unbelievers are led to wrong thereby: for they make it lawful one year, and forbidden another year, of months forbidden by Allah and make such forbidden ones lawful. The evil of their course seems pleasing to them. But Allah guideth not those who reject Faith.

Certainly the Nasi is an impious addition, which has led the infidels into error. One year they authorise the Nasi, another year they forbid it. They observe the divine precept with respect to the number of the sacred months, but in fact they profane that which God has declared to be inviolable, and sanctify that which God has declared to be profane. Assuredly time, in its revolution, has returned to such as it was at the creation of the heavens and the earth. In the eyes of God the number of the months is twelve. Among these twelve months four are sacred, namely, Rajab, which stands alone, and three others which are consecutive.

The three successive forbidden months mentioned by Muhammad (months in which battles are forbidden) are Dhu al-Qi'dah, Dhu al-Hijjah, and Muharram, months 11, 12, and 1. The single forbidden month is Rajab, month 7. These months were considered forbidden both within the new Islamic calendar and within the old pagan Meccan calendar, although whether they maintained their "forbidden" status after the conquest of Mecca has been disputed among Islamic scholars.[citation needed]

In pre-Islamic Arabia, it was customary to identify a year after a major event which took place in it. Thus, according to Islamic tradition, Abraha, governor of Yemen, then a province of the ChristianKingdom of Aksum (Ethiopia), attempted to destroy the Kaaba with an army which included several elephants. The raid was unsuccessful, but that year became known as the Year of the Elephant. It saw the birth of Muhammad (see suratal-Fil). That corresponded to the year 570 or 571 CE.

In 638 (the year 17 AH), Abu-Musa al-Asha'ari, one of the officials of the second Caliph Umar in Basrah, complained about the absence of any dating system in the correspondence he received from Umar, making it difficult for him to determine which instructions were most recent. This report convinced Umar of the need to introduce a calendar system for Muslims. After debating the issue with his Counsellors, he decided to start the calendar with the date of Muhammad’s arrival at Medina.

Uthman ibn Affan then suggested to start the calendar with the month of Muharram, in line with the established custom of the Arabs at that time.

The Islamic calendar numbering of the years thus began with the month of Muharram in the year of Muhammad’s arrival at the city of Medina. According to calculations, the first day of the first year corresponded to Friday, July 16, 622 (even though the actual emigration took place in September).[1] Because of the Hijra event, the calendar was named the Hijra calendar.[13]

The first surviving attested use of the Hijri calendar is on a papyrus from Egypt in 22 AH, PERF 558.

The Islamic calendar is not to be confused with the lunar calendar. The latter is based on a year of 12 months adding up to 354.37 days. Each lunar month begins at the time of the monthly "conjunction", when the Moon is located on a straight line between the Earth and the Sun. The month is defined as the average duration of a rotation of the Moon around the Earth (29.53 days). By convention, months of 30 days and 29 days succeed each other, adding up over two successive months to 59 full days. This leaves only a small monthly variation of 44 mn to account for, which adds up to a total of 24 hours (i.e. the equivalent of one full day) in 2.73 years. To settle accounts, it is sufficient to add one day every three years to the lunar calendar, in the same way that one adds one day to the Gregorian calendar, every four years.[14] The technical details of the adjustment are described in Tabular Islamic Calendar.

The Islamic calendar, however, is based on a different set of conventions.[15] Each month has either 29 or 30 days, but usually in no discernible order. Traditionally, the first day of each month is the day (beginning at sunset) of the first sighting of the hilal shortly after sunset. If the hilal is not observed immediately after the 29th day of a month (either because clouds block its view or because the western sky is still too bright when the moon sets...), then the day that begins at that sunset is the 30th. Such a sighting has to be made by one or more trustworthy men testifying before a committee of Muslim leaders. Determining the most likely day that the hilal could be observed was a motivation for Muslim interest in astronomy, which put Islam in the forefront of that science for many centuries.

This traditional practice is still followed in the overwhelming majority of Muslim countries. Each Islamic State proceeds with its own monthly observation of the new moon (or, failing that, awaits the completion of 30 days) before declaring the beginning of a new month on its territory. But, the lunar crescent becomes visible only some 15–18 hours after the conjunction, and only subject to the existence of a number of favourable conditions relative to weather, time, geographic location, as well as various astronomical parameters.[16] Given the fact that the moon sets progressively later than the sun as one goes West, Western Muslim countries are likely to observe the new moon one day earlier than Eastern Muslim countries. Due to the interplay of all these factors, the beginning of each month differs from one Muslim country to another, and the information provided by the calendar in any country does not extend beyond the current month.

A number of Muslim countries try to overcome some of these difficulties by applying different astronomy-related rules to determine the beginning of months. Thus, Malaysia, Indonesia, and a few others begin each month at sunset on the first day that the moon sets after the sun (moonset after sunset). In Egypt, the month begins at sunset on the first day that the moon sets at least five minutes after the sun...A detailed analysis of the available data shows, however, that there are major discrepancies between what countries say they do on this subject, and what they actually do.[17]

If the Islamic calendar were prepared using astronomical calculations, Muslims throughout the Muslim world could use it to meet all their needs, the way they use the Gregorian calendar today. But, there are divergent views on whether it is licit to do so.[18]

A majority of theologians oppose the use of calculations on the grounds that the Qur'an requires direct sighting in Surah al-Baqarah 2:185 [19] and that calculations would not conform with Muhammad's recommendation to observe the new moon of Ramadan and Shawal in order to determine the beginning of these months.[20]

Some jurists see no contradiction between Muhammad’s teachings and the use of calculations to determine the beginnings of lunar months.[21] They consider that Muhammad's recommendation was adapted to the culture of the times, and should not be confused with the acts of worship.[22][23][24]

Thus, jurists Ahmad Muhammad Shakir and Yusuf al-Qaradawi both endorsed the use of calculations to determine the beginning of all months of the Islamic calendar, in 1939 and 2004 respectively.[25][26] So did the "Fiqh Council of North America" (FCNA) in 2006[27][28] and the "European Council for Fatwa and Research" (ECFR) in 2007.[29]

Saudi Arabia uses the sighting method to determine the beginning of each month of the Hijri calendar. Since AH 1419 (1998/99) several official hilal sighting committees have been set up by the government to determine the first visual sighting of the lunar crescent at the beginning of each lunar month. Nevertheless, the religious authorities also allow the testimony of less experienced observers and thus often announce the sighting of the lunar crescent on a date when none of the official committees could see it.

The country also uses the Umm al-Qura calendar, based on astronomical calculations, but this is restricted to administrative purposes. The parameters used in the establishment of this calendar underwent significant changes over the past decade.[30]

Before AH 1420 (before April 18, 1999), if the moon's age at sunset in Riyad was at least 12 hours, then the day ending at that sunset was the first day of the month. This often caused the Saudis to celebrate holy days one or even two days before other predominantly Muslim countries, including the dates for the Hajj, which can only be dated using Saudi dates because it is performed in Mecca.

For AH 1420-22, if moonset occurred after sunset at Mecca, then the day beginning at that sunset was the first day of a Saudi month, essentially the same rule used by Malaysia, Indonesia, and others (except for the location from which the hilal was observed).

Since the beginning of AH 1423 (March 16, 2002), the rule has been clarified a little by requiring the geocentric conjunction of the sun and moon to occur before sunset, in addition to requiring moonset to occur after sunset at Mecca. This ensures that the moon has moved past the sun by sunset, even though the sky may still be too bright immediately before moonset to actually see the crescent.

In 2007, the Islamic Society of North America, the Fiqh Council of North America and the European Council for Fatwa and Research announced that they will henceforth use a calendar based on calculations, using the same parameters as the Umm al-Qura calendar, to determine (well in advance) the beginning of all lunar months (and therefore the days associated with all religious observances). This was intended as a first step on the way to unify Muslims' calendars throughout the world, in some future time. But, despite this stated objective, they will continue to differ, on this point, from Saudi Arabia's officially stated, but hard to verify policy of relying exclusively on sighting to determine the dates of religious observances.[31][32]

There exists a variation of the Islamic calendar known as the tabular Islamic calendar in which months are worked out by arithmetic rules rather than by observation or astronomical calculation. It has a 30-year cycle with 11 leap years of 355 days and 19 years of 354 days. In the long term, it is accurate to one day in about 2500 years. It also deviates up to about 1 or 2 days in the short term.

Microsoft uses the "Kuwaiti algorithm" to convert Gregorian dates to the Islamic ones. Microsoft claims that it is based on a statistical analysis of historical data from Kuwait[33] but it is in fact a variant of the tabular Islamic calendar.[34]

For a very rough conversion, multiply the Islamic year number by 0.97, and then add 622 to get the Gregorian year number. An Islamic year will be entirely within a Gregorian year of the same number in the year 20874. The Islamic calendar year of 1429 occurred entirely within the Gregorian calendar year of 2008. Such years occur once every 33 or 34 Islamic years (32 or 33 Gregorian years). More are listed here:

Islamic year within Gregorian year

Islamic

Gregorian

Difference

1060

1650

590

1093

1682

589

1127

1715

588

1161

1748

587

1194

1780

586

1228

1813

585

1261

1845

584

1295

1878

583

1329

1911

582

1362

1943

581

1396

1976

580

1429

2008

579

1463

2041

578

1496

2073

577

1530

2106

576

1564

2139

575

Because a hijri or Islamic lunar year is between 10 and 12 days shorter than a Gregorian year, it begins 10–12 days earlier in the Gregorian year following the Gregorian year in which the previous hijri year began. Once every 33.58 hijri years, or once every 32.58 Gregorian years, the beginning of a hijri year (1 Muharram) coincides with one of the first ten days of January. Subsequent hijri New Years move backward through the Gregorian year back to the beginning of January again, passing through each Gregorian month from December to January. To find the Gregorian year and approximate Gregorian month within which a specific hijri year begins, locate that hijri year within the table above. Subtract from it the hijri year after the previous hijri year which occurred within a single Gregorian year (the coinciding year). For the hijri year 1344, the previous coinciding hijri year was 1329, so subtract 1330 from 1344, yielding 14. Add 14 to the coinciding Gregorian year of 1911 yielding 1925. To determine the approximate Gregorian month within which the stated hijri year begins, divide 14 by 33 (the coincidence period) and multiply by 12 months yielding 5.5 months before January. Thus hijri year 1330 begins within July 1925.

The Islamic calendar is now used primarily for religious purposes, and for official dating of public events and documents in Muslim countries. Because of its nature as a purely lunar calendar, it cannot be used for agricultural purposes and historically Islamic communities have used other calendars for this purpose: the Egyptian calendar was formerly widespread in Islamic countries, and the Iranian calendar and the 1789 Ottoman calendar (a modified Julian calendar) were also used for agriculture in their countries. In Morocco, the Berber calendar (another Julian calendar) is still used by farmers in the countryside. These local solar calendars have receded in importance with the near-universal adoption of the Gregorian calendar for civil purposes. As noted above, Saudi Arabia uses the Islamic calendar to date religious occasions such as Ramadan, Hajj, etc. and the Umm-al-Qura calendar, based on calculations, for administrative purposes and daily government business.[35]

↑The dynasty of Fatimids in Egypt used a tabular pre-calculated calendar over a period of two centuries, between the 10th and 12th centuries, before a change of political regime reactivated the procedure of observation of the new moon.